This invention relates in general to electrostatographic reproduction machines, and more particularly to an extended life and recycleable silencer assembly for reducing screeching noises between a cleaning blade and an imaging member of an electrostatographic reproduction machine.
Electrostatographic imaging members are well known in the art. The imaging members may be in the form of various configurations such as a flexible web type belt or cylindrical drum. The drums comprise a hollow cylindrical substrate and at least one electrostatographic coating. These drums are usually supported by a hub held in place at the end of the drum. The hub usually includes a flange that extends into the interior of the drum and is usually retained in place by an adhesive. An axle shaft through a hole in the center of the hub supports the hub and drum assembly.
Electrostatographic imaging members as such may be electrostatographic or electrographis members. It is well known that electrostatographic members comprise at least one photosensitive imaging layer and are imaged with the aid of activating radiation in image configuration whereas electrographic imaging members comprise at least one dielectric layer upon which an electrostatic latent image is formed directly on the imaging surface by shaped electrodes, ion streams, styli and the like. A typical electrnstatographic imaging process cycle involve storming an electrostatic latent image on the imaging surface, developing the electrostatic latent image to form a toner image, transferring the toner image to a receiving member and cleaning the imaging surface. Cleaning of the imaging surface of electrostatographic imaging members is often accomplished with a doctor type resilient cleaning blade that is rubbed against the imaging surface of the imaging members.
When electrostatographic imaging member are cleaned by doctor type cleaning blades rubbing against the imaging surface to remove residual toner particles remaining on the imaging surface after toner image transfer to a receiving member, a high pitched ringing, squealing, squeaking, or howling sound can be created which is so intense that it is intolerable for machine operators. This is especially noted in drum type imaging members comprising a hollow cylindrical substrate. The sound apparently is caused by a xe2x80x9cstick-slipxe2x80x9d cycling phenomenon during which the cleaning blade initially xe2x80x9csticksxe2x80x9d to the imaging surface and is carried in a downstream direction by the moving imaging surface to a point where resilience of the imaging blade forces the tucked blade to slip and slide back upstream where it again sticks to the imaging member and is carried downstream with the imaging surface until blade resilience again causes the blade to flip back to its original position.
The upstream flipping motion kicks residual toner particles forward. The stick-slip phenomenon is somewhat analogous to the use of a push broom for cleaning floors where the push broom is most effective for cleaning when it is pushed a short distance and then tapped on the floor with the cycle being repeated again and again. This stick-slip phenomenon is important for effective removal of residual untransferred toner particles from an imaging surface and for prevention of undesirable toner film or toner comets from forming on the imaging surface during cleaning.
An adhesive relationship between the cleaning blade and the imaging member surface appears to contribute to the creation of the ringing, squealing, squeaking, or howling sound. More specifically, the stick-slip effect occurs where there is a strong adhesive interaction between the cleaning blade and the imaging surface. The ringing, squealing, squeaking, or howling sound appears to be caused by resonant vibration of the drum induced by the stick-slip phenomenon. Other factors contributing to creation of the ringing, squealing, squeaking, or howling sound may include factors such as the construction of the imaging member, the blade contacting the imaging member, the type of blade holder construction, and the like. For example, a flimsy blade holder can contribute to the howling effect. Moreover, a thinner, shorter, stubbier cleaning blade tends to contribute to the howling effect. Thin imaging member drums can also lead to the howling effect.
The stick-slip phenomenon also depends on the lubricating effect of toner and/or carrier materials utilized. Moreover, ambient temperatures can contribute to the creation of howling. It appears that resonance is initiated at the point of contact between the cleaning blade and the imaging member. The creation of the squealing or howling sound might be analogous to rubbing a fingertip around the edge of a wine glass. The squealing or howling noise phenomenon is especially noticeable for cylindrical photoreceptors having a hollow metal or plastic drum shaped substrate. Generally, where the imaging member is the cause of a howling sound, it will emit a ringing sound when tapped.
These sounds cannot be tolerated in a office environment. To overcome this drawback, various devices have been developed which can be inserted inside the hollow drum to dampen the drum and diminish or eliminate all irritating sounds emitted during an imaging operation. Some of these devices include, for example, porous members which are compressed when inserted inside a hollow photoreceptor drum to perform a sound deadening function while pressing against the inner surface of the drum. Examples of this type of sound dampener are described, in U.S. patent application No. 5,722,016, Japanese Patent Publication 63060481, published Mar. 16, 1998 and Japanese Patent Publication 63271388, published Nov. 9, 1998.
Another such device for preventing undesirable sounds in a drum photoreceptor includes a control member having a xe2x80x9cCxe2x80x9d cross-section. This type of device is described, for example, in Japanese Patent Publication 02118684, published May 2, 1990. This device is difficult to compress and slide into a hollow drum unless the control member is very thin. A very thin control member may not have sufficient mass to dampen any squeaking sound. However, thicker silencer members having a xe2x80x9cCxe2x80x9d shaped cross-section may be utilized if modified to form a hinge of thinner material extending axially along the length of the xe2x80x9cCxe2x80x9d shaped member. The hinge of thinner material is preferably located opposite the gap of the xe2x80x9cCxe2x80x9d shaped member. This hinge allows a relatively thick silencer to be more easily squeezed so that the exposed ends at the longitudinal gap come together to form a silencer having a smaller cross-section thereby allowing the silencer to be inserted into the hollow drum. This arrangement also facilitates removal of the silencer from the drum for recycling.
Unfortunately, it has been found that where a silencer having a xe2x80x9cCxe2x80x9d shaped cross-section and a hinge is utilized in a photoreceptor drum that has been cycled many thousands of cycles, the cross-sectional area of the silencer becomes smaller due to the silencer taking a xe2x80x9csetxe2x80x9d while it""s in the compressed mode within the interior of the drum. Thus, upon removal of the silencer for recycling and use in a fresh drum, the silencer loses its effectiveness for dampening sounds due to insufficient pressure contact between the silencer and the interior of the drum. Both the outside diameter and inside diameter of the xe2x80x9cCxe2x80x9d shaped silencer become smaller with use. Such reduction is believed to be the result of plastic deformation while under partial compression in the interior of a hollow photoreceptor drum. Thus, over time, such silencers, e.g. PVC silencers, become relaxed and no longer apply outward pressure to the inside diameter of the silencer. This causes the silencer to rattle within the photoreceptor causing more noise.
Thus, there is a continuing need for an extended life and recycleable silencer assembly for reducing screeching noises between a cleaning blade and the imaging member of an electrostatographic reproduction machine.
In accordance with the present invention, there is provided a silencer assembly that has an extended life, is recycleable and suitable for reducing screeching noises between a cleaning blade and an imaging member of an electrostatographic reproduction machine. The silencer assembly includes (i) a first C-shaped member comprising a wall defining a slot extending axially in the wall, and an interior cavity having a predetermined inside diameter in the free state, (ii) at least one partially compressed high density polymeric open cell foam plug inserted into a portion of the interior cavity, and (iii) a replaceable second C-shaped member inserted within the interior cavity for reducing plastic deformation of the first C-shaped member, thereby extending life of the silencer assembly and making the silencer assembly easily recyclable.